Agro-industrial residues and starch for growth and co-production of polyhydroxyalkanoate copolymer and α-amylase by Bacillus sp. CFR-67

Polyhydroxyalkanoates (PHA) and α-amylase (α-1,4 glucan-4-glucanohydrolase, E.C. 3.2.1.1) were co-produced by Bacillus sp. CFR-67 using unhydrolysed corn starch as a substrate. Bacterial growth and polymer production were enhanced with the supplementation of hydrolysates of wheat bran (WBH) or rice bran (RBH) individually or in combination (5-20 g L(-1), based on weight of soluble substrates-SS). In batch cultivation, a mixture of WBH and RBH (1:1, 10 g L(-1) of SS) along with ammonium acetate (1.75 g L(-1)) and corn starch (30 g L(-1)) produced maximum quantity of biomass (10 g L(-1)) and PHA (5.9 g L(-1)). The polymer thus produced was a copolymer of polyhydroxybutyrate-co-hydroxyvalerate of 95:5 to 90:10 mol%. Presence of WBH and corn starch (10-50 g L(-1)) in the medium enhanced fermentative yield of α-amylase (2-40 U mL(-1) min(-1)). The enzyme was active in a wide range of pH (4-9) and temperature (40-60°C). This is the first report on simultaneous production of copolymer of bacterial PHA and α-amylase from unhydrolysed corn starch and agro-industrial residues as substrates.